Field of the Invention
The invention relates to an arrangement having a superconducting cable, which comprises a superconducting conductor and a superconducting screen which concentrically surrounds the same with the interposition of a dielectric, which cable is surrounded by a cryostat, enclosing a free space for a coolant to be passed through, which cryostat comprises two metallic tubes which are arranged concentrically with respect to one another and between which vacuum insulation is arranged (WO 03/052775 A1).
Description of Related Art
In modern technology, a superconducting cable has electrical conductors composed of a composite material which contains ceramic material which changes to the superconducting state at sufficiently low temperatures. The electrical direct-current resistance of a correspondingly designed conductor is zero when adequate cooling is provided, provided that a specific current level is not exceeded. By way of example, suitable ceramic materials are YBCO (yttrium-barium-copper oxide) or BSCCO (bismuth-strontium-calcium-copper oxide). By way of example, sufficiently low temperatures to change a material such as this to the superconducting state are between 67 K and 110 K. By way of example, suitable coolants are nitrogen, helium, neon and hydrogen or mixtures of these substances.
In the arrangement according to the initially cited WO 03/052775 A1, a superconducting cable is used with a cold dielectric. This comprises an inner conductor, which is applied to a tubular support, and a screen which is arranged concentrically with respect thereto, which are held separated from one another and at a distance by the dielectric (insulation). By way of example, the conductor and the screen are composed of strips of superconducting material, such as YBCO or BSCCO, which are wound around a substrate, lying closely alongside one another, with a long lay length. This known superconducting cable is designed such that the superconducting screen externally screens the magnetic field of the superconducting conductor during fault-free operation. The cable impedance changes only insignificantly when a short circuit occurs. The short-circuit current results in a large amount of energy being introduced, to be precise both into the conductor and into the screen of the cable, which can lead to destruction (burn-out) of the cable.